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feat(minifier): dce meaningless labeled statements (#6688)

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This commit is contained in:
7086cmd 2024-10-19 15:48:54 +00:00
parent e1c2d30d44
commit 34fe7c00a3
1 changed files with 29 additions and 5 deletions
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34
crates/oxc_minifier/src/ast_passes/peephole_remove_dead_code.rs
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@ -38,6 +38,7 @@ impl<'a> Traverse<'a> for PeepholeRemoveDeadCode {
Statement::ExpressionStatement(expr_stmt) => {
Self::try_fold_expression_stmt(expr_stmt, ctx)
}
Statement::LabeledStatement(labeled) => Self::try_fold_labeled(labeled, ctx),
_ => None,
} {
*stmt = new_stmt;
@ -235,6 +236,30 @@ impl<'a, 'b> PeepholeRemoveDeadCode {
}
}
/// Remove meaningless labeled statements.
///
/// ```js
/// a: break a;
/// ```
fn try_fold_labeled(
labeled: &mut LabeledStatement<'a>,
ctx: Ctx<'a, 'b>,
) -> Option<Statement<'a>> {
let id = labeled.label.name.as_str();
// Check the first statement in the block, or just the `break [id] ` statement.
// Check if we need to remove the whole block.
match &mut labeled.body {
Statement::BreakStatement(break_stmt)
if break_stmt.label.as_ref().is_some_and(|l| l.name.as_str() == id) => {}
Statement::BlockStatement(block) if block.body.first().is_some_and(|first| matches!(first, Statement::BreakStatement(break_stmt) if break_stmt.label.as_ref().is_some_and(|l| l.name.as_str() == id))) => {}
_ => return None,
}
let mut var = KeepVar::new(ctx.ast);
var.visit_statement(&labeled.body);
let var_decl = var.get_variable_declaration_statement();
var_decl.unwrap_or(ctx.ast.statement_empty(SPAN)).into()
}
fn try_fold_expression_stmt(
stmt: &mut ExpressionStatement<'a>,
ctx: Ctx<'a, 'b>,
@ -322,12 +347,12 @@ impl<'a, 'b> PeepholeRemoveDeadCode {
);
}
return Some(ctx.ast.statement_expression(
Some(ctx.ast.statement_expression(
array_expr.span,
ctx.ast.expression_from_sequence(
ctx.ast.sequence_expression(array_expr.span, transformed_elements),
),
));
))
}
// `{a: 1, b: 2, c: foo()}` -> `foo()`
@ -413,12 +438,12 @@ impl<'a, 'b> PeepholeRemoveDeadCode {
);
}
return Some(ctx.ast.statement_expression(
Some(ctx.ast.statement_expression(
object_expr.span,
ctx.ast.expression_from_sequence(
ctx.ast.sequence_expression(object_expr.span, filtered_properties),
),
));
))
}
/// Try folding conditional expression (?:) if the condition results of the condition is known.
@ -497,7 +522,6 @@ mod test {
}
#[test]
#[ignore]
fn test_remove_no_op_labelled_statement() {
fold("a: break a;", "");
fold("a: { break a; }", "");